The invention is based on an electrical drive mechanism, particularly for motor vehicles, according to the preamble to claim 1.
In a known electrical drive mechanism of the type mentioned the beginning (U.S. Pat. No. 3,624,434), the commutator-end bearing is embodied as a dome-shaped bearing and is disposed inside a recess of a cap-shaped housing part. The bearing scat for the spherical segment-shaped bearing bush is constituted by an annular securing spring, which is inserted with an annular edge into the recess and, with a multitude of resilient fingers, which constitute the bearing seat, overlaps the half of the bearing bush oriented away from the commutator. As a result, the securing spring rests with an annular collar against the housing part and is clamped against the housing wall by a fastening plate, which supports the brush holder and has an opening coaxial to the rotor shaft, so that the securing spring is fixed in the recess of the housing part. The half of the bearing bush oriented toward the brush holder is overlapped by resilient fingers of a second securing spring, which constitutes the clamping member and is clipped into the opening of the fastening plate, where a collar of outer fingers engages behind the fastening plate and the securing spring is clamped to the fastening plate so that the inner resilient fingers exert an axial pressure on the bearing bush.
The electrical drive mechanism according to the engine has the advantage that the commutator-end bearing of the rotor shaft is comprised of only a few components, namely the bearing bush and the clamping member that constitutes an integral component of the brush holder. The bearing seat is produced already in the production of the housing so that it incurs no additional manufacturing expenditure. Since the clamping member is a component of the brush holder, the assembly of the drive mechanism is significantly simplified. The rotor shaft, which is equipped with an armature winding, commutator, brush holder, and bearing bush, is slid into the housing and in so doing, the bearing bush is inserted into the bearing seat, as a result of which the brush holder and therefore also the bearing bush are secured in place in the bearing seat. With that, the assembly is already finished. The assembly process can easily be automated with no trouble.
Advantageous modifications and improvements of the electrical drive mechanism disclosed in claim 1 are possible through the steps taken in the remaining claims.
According to a preferred embodiment of the invention, the clamping member is constituted by means of two spring-elastic securing arms, which are disposed on the brush holder and extend parallel to the rotor shaft on diametrically opposed sides of it and are supported with their free ends against contact bevels provided on the bearing bush, which bevels are embodied as inclined at an acute angle in relation to the rotor shaft on the side of the bearing bush oriented toward the brush holder. By embodying the bearing of the rotor shaft as a dome-shaped bearing, the contact bevels are constituted by circumference regions of the spherical segment-shaped bearing bush.
According to an advantageous embodiment of the invention, an annular fitting, which has a defined internal diameter and is supported in front of the bearing seat, is incorporated into the housing, and the free ends of the securing arms are inserted into this annular fitting. This annular fitting prevents the spring-elastic securing arms from splaying outward when being slid onto the bearing bush so that the securing arms exert a compressive force with an axial force component onto the bearing bush, which fixes the bearing bush in the bearing seat in a frictionally engaged manner. This frictional engagement between the bearing bush and the bearing seat prevents the rotor- or armature shaft from causing the bearing bush to rotate along with it, which would generate noise or cause a malfunction.
According to an advantageous embodiment of the invention, the bearing bush is also reliably prevented from rotating in the bearing seat along with the rotor shaft through the embodiment of reciprocally matched form-fitting elements on the bearing bush and bearing seat. For example, form-fitting elements can be provided on the surface of the bearing bush, which cooperate with matched opposing contours on the bearing seat and/or on the securing arms and as a result, secure the bearing bush in the bearing seat in a non-rotating manner. These form-fitting elements can be beads or flattenings. When the bearing of the rotor shaft is embodied as a dome-shaped bearing, the opposing contours must offer the possibility of being able to adapt to an inclined position of the armature shaft.
According to an advantageous embodiment of the invention, an arc-shaped slot is let into the end of each of the two securing arms. This slotting of the securing arms in their end regions can compensate for tolerances occurring in the axial and radial direction.